1. Field of the Invention
This invention relates to medical devices. Specifically, but not by way of limitation, this invention relates to medical devices for introduction of a media such as cells into a body cavity, such as within the human brain.
2. Background
In this document, the medical device that is described is inserted within a body cavity. While the insertion procedure could be directed at any of several locations within a patient, for the discussion in this document, a neurosurgical procedure will be used as an example. Assisting devices may also be used in combination with the present insertion device in a neurosurgical procedure. Such devices may include, but are not limited to, a stereotactic headframe, a trajectory guide, electronic tissue imaging equipment, and frameless reference systems.
A common surgical technique inserts a medical device into a patient to a targeted area through a small opening that is surgically opened in the patient. Inserting a device to the targeted area of the patient and disturbing as little tissue as possible is a high priority. Small openings are desirable because they are less invasive and less traumatic to the patient. A catheter is a broad category of medical devices that can be inserted into a patient through small openings. The term catheter could include several configurations of devices. In one basic form, a catheter includes a hollow tube, or passage to deliver a media such as a drug or other treatment media to a selected location in the patient. Included in the general definition of catheters are multiple tube devices. Multiple tube configurations typically include an outer tube, and an inner tube, where one of the tubes is moveable with respect to the other tube.
In this document, references to coordinates with respect to catheters or insertion devices will refer to axial or longitudinal locations and radial locations. Axial or longitudinal locations are typically locations with reference to an insertion axis. Radial locations will use the conventional 2-dimensional radial coordinates (r, θ) in a circle that is normal to the insertion axis. By combining an axial coordinate with the radial coordinates, a point can be located in three dimensional space relative to a given reference frame, such as the patient. Descriptions of the insertion axis in this document will generally refer to depth inside a patient along a line. It should be noted that although catheters need not be inserted along a straight line, a generally linear depth model will be used for ease of discussion. Also, the axial end, or tip of the catheter that is inserted into a patient is referred to herein as the distal end of the catheter, while the axial end of the catheter that remains toward the outside the patient is referred to as the proximal end.
In some medical procedures, it is desirable to distribute a media over a large target area within a patient. One procedure that utilizes a large distribution target area is neurosurgical cell therapy. Several prior approaches have been used to accomplish a large distribution target area. In one approach, a relatively small catheter, such as a single lumen catheter, is inserted into a patient several consecutive times. In this procedure, a measured amount of media, or dose, is delivered at one location, and then the catheter is withdrawn and re-inserted at a nearby location to deliver another dose. This process is repeated a number of times until the entire target area has received the desired dose. A problem with this approach is that multiple insertions disturb a large amount of tissue in the patient. Each time that tissue is disturbed, there is a chance for tissue damage.
Some catheters utilize a single lumen host catheter that houses a delivery catheter having a deflected distal tip. The deflected distal tip exits the single lumen host catheter in a direction chosen by the orientation of the single lumen host catheter upon insertion. The deflected distal tip slightly increases the distribution of a single insertion and dose, however larger target area coverage is still needed. Steerable catheters exist, where the orientation and location of the distal tip can be changed while the distal tip is inserted in the patient, however, moving the distal tip while it is within the patient further disturbs tissue, which again, can lead to tissue damage. Also, steerable catheters are typically more complex and expensive to manufacture.
Another approach has been to insert a relatively large host catheter, the host catheter incorporating a number of internal passages for micro-catheters. The internal passages exit a distal end of the large host catheter at a distribution of locations around the distal end. Using this approach, the large host catheter is inserted in a center of the target area. Micro-catheters are then inserted in the various internal passages, and a dose is delivered at each of the distribution of locations. In this way a larger target area is covered without the need for multiple host catheter insertions. A problem with this approach is that the large host catheter displaces a large amount of tissue, even though the number of insertions is reduced.
What is needed is a device and method for distributing a media over a large target area. What is further needed is a device and method that disturbs a lower amount of tissue.